Intrinsic factors of traumatic anterior shoulder instability due to minor injury

Abstract

Background: We hypothesized that the glenohumeral joint morphology as an intrinsic factor was related to the onset of shoulder instability due to minor injury. The purpose of this study was to clarify the relationship between gender, shoulder laxity and the glenohumeral morphology and the onset of traumatic anterior shoulder instability due to minor injury.
Methods: We examined 125 shoulders of 125 patients (89 males, 36 females) with traumatic anterior shoulder instability who had pre-operative computed tomography. The mean age was 27 years old (14-64). According to the mechanism of the onset of shoulder instability, the patients were divided into 2 groups, traumatic group and minor injury group. The evaluation items of intrinsic factors were gender, laxity and the glenohumeral joint morphology. The maximum transverse diameters of the articular surface of the glenoid and the maximum diameters of the humeral head were measured and the glenoid-head ratio (GH ratio) was calculated on CT in the unaffected shoulder. Gender, laxity and GH ratio were compared between the 2 groups.
Results: The number of females in the minor injury group; 46.7% was significantly more than that in the traumatic group; 12.3%. There was no significant difference between the GH ratio in the traumatic group; 63.9% and that in minor injury group; 62.4%. However, the G-H ratio in females; 61.3% was significantly smaller than that in males; 63.9%.
Conclusion: Being female and having a small GH ratio might be the intrinsic factors of traumatic anterior shoulder instability due to minor injury.